Case #501 - October, 2019
A 72-year-old woman originally from China presented to a clinic with complaints of abdominal pain, nausea, vomiting, and diarrhea over one week. She also reported that she experienced bouts of abdominal discomfort over the past year. Endoscopic retrograde cholangiopancreatography (ERCP) was performed, which demonstrated a live parasite in the common bile duct. The parasite was removed, embedded in paraffin, sectioned, and stained with hematoxylin and eosin (H&E). Shown below are images of the sectioned organism (Figure A is taken at 20x magnification; Figure B is taken at 200x magnification; scale bars are provided on Figures C and D).
What is your diagnosis? Based on what features?
This case was kindly contributed by the California Pacific Medical Center.
This is a case of dicrocoeliasis. Two species of Dicrocoelium may infect humans; D. dendriticum is the most likely species as it occurs worldwide, whereas D. hospes appears restricted to West Africa. Among flukes infecting the human biliary tract, Dicrocoelium is a much less frequently encountered than Fasciola, Clonorchis, and Opisthorchis. Diagnosis is most commonly based on detection of eggs shed in stool, although rarely, adult flukes may be recovered in cases such as this one.
Diagnostic features shown include:
- thick-shelled, relatively small (35—45 µm) eggs
- presence of very inconspicuous shoulders (arrows) and operculum on one pole of eggs (these features may only be apparent in cross-sections)
- differentiated miracidia within eggs
- aspinous tegument
Eurytrema pancreaticum is a related zoonotic trematode that has nearly identical eggs (thus, this answer was acceptable); however, the normal location in the host is the pancreas and this is very rarely present in the bile duct.
More on: Dicrocoeliasis
Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.
DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.